Amplifier control circuit



May 19, 1964 D. R. GRAEF AMPLIFIER CONTROL cmcun Filed Oct. 31, 1960 Fi l.

Fig. 2.

mmvroa DANIEL R. GRAEF BY Mwmam 121M United States Patent Daniel R. Graefi, Fort Wayne, Ind, assignor to The Ii KfigmWGX tlompany, Fort Wayne, End, a corporation of Delaware Filed Get. 31, 1969, Ser. No. 66,287 2 Ciaims. (tCl. 179-=-1) This invention is related generally to sound systems and more particularly to control of bass frequencies in radio receivers and sound systems including stereo sound reproduction systems.

In the past various means have been employed in sound systems to minimize low frequency noises such as those manifesting themselves as turntable rumble and feedback. However, a control of bass frequency is desirable to provide the individual listener with means of adjusting the sound to best suit his individual hearing taste. He can therefore make appropriate adjustments to avoid noise such as turntable rumble without sacrificing too many of the lows. At the same time it is desirable that any such control be relatively simple and inexpensive. Moreover, functionally the control must accommodate channel separation, highest possible circuit gain, balance at various bass control and volume control settings, and phased pickup elements.

It is therefore a general object of this invention to provide for a sound system means whereby an individual listener can adjust the sound to his particular individual taste.

It is another object of this invention to provide a control for multi-channel sound systems which accommodates channnel separation.

It is a further object of this invention to provide a control for sound systems which does not upset balance at various control settings and which is adapted to use with phased pickup elements in the sound reproduction system application.

It is still another object of this invention to accomplish the foregoing objects by simple and inexpensive means.

This invention as applied to a multi-channel sound system consists of tapping off between the separate sound inputs and attaching a variable resistance between the tap and a ground. The variable resistance makes possible varying the amount of bass output from both channels simultaneously.

The full nature of the invention will be understood from the accompanying drawings and the following description and claims:

FIG. 1 shows this invention as applied to a two channel phonograph.

FIG. 2 shows this invention as applied to a sterophonic radio input circuit.

Referring to FIG. 1 there is shown a phonograph cartridge designated generally by the reference numeral 11 having a stylus 12 and a ground connection 13. The cartridge 11 has two outputs 14 and 16 coupled to a first amplifier channel 17 and a second amplifier channel 18 having loudspeakers 19 and 20, respectively. A voltage divider 21 comprised of resistors 22 and 23 having Fatented May 19, 1%64 the common junction 24 is connected across the outputs 14 and 16. A variable resistance 26 having a movable tap Z7 is attached between the common junction 2 and ground 13. By moving the variable tap, the amount of bass output from both channels can be varied simultaneous-y.

FIG. 2 is identical in form to FIG. 1 with the exception that the inputs to the channels 17 and 13 are provided through the coupling capacitors 34 and 36 to couple radio input signals from terminals 37 and 38 to the sound system incorporating the channels 17 and 18. Again, as with the case of PEG. 1, the bass frequency outputs can be varied simultaneously by adjustment of the movable tap 27 of the variable resistor 26.

While the invention has been disclosed and described in some detail in the drawings and foregoing description, they are to be considered as illustrative and not restrictive in character, as modifications may readily suggest themselves to persons skilled in this art and within the broad scope of the invention, reference being had to the appended claims.

The invention claimed is:

1. A bass control for a stereo phonograph system comprising: a stereophonic phonograph pickup cartridge having first and second outputs for stereo signals, said cartridge having inherent capacitance between said outputs and ground; a pair of resistors joined in a serial coupling across said outputs, said resistors being connected together to provide a junction; and a variable resistor coupled to said junction between said resistors, said variable resistor having an adjustable wiper connected to ground, said pair of resistors, said variable resistor and said inherent capacitance providing variable resistancecapacitance circuits to control bass frequencies.

2. A stereo sound reproducing system comprising: a phonograph pickup cartridge having dual outputs for two stereo signal channels, an amplifier channel coupled to each of said outputs for providing two stereo signal channels, bass control circuit means comprising a pair of resistors coupled in series between said outputs, and a variable resistor coupled to the junction of said resistors and having an adjustable wiper connected to ground, said pickup cartridge having inherent capacitance between each output and ground, the inherent capacitance of one output being in series with one of said pair of resistors and with said variable resistor to complete a first bass control circuit for one of said stereo signal channels, and the inherent capacitance of the other output being in series with the other of said pair of resistors and with said variable resistor to complete a second bass control circuit for the other of said stereo signal channels, the bass output of both channels being controllable simultaneously by variation of said variable resistor.

High, Fidelity Magazine, April 1959, pages 109, 126. 

1. A BASS CONTROL FOR A STEREO PHONOGRAPH SYSTEM COMPRISING: A STEREOPHONIC PHONOGRAPH PICKUP CARTRIDGE HAVING FIRST AND SECOND OUTPUTS FOR STEREO SIGNALS, SAID CARTRIDGE HAVING INHERENT CAPACITANCE BETWEEN SAID OUTPUTS AND GROUND; A PAIR OF RESISTORS JOINED IN A SERIAL COUPLING ACROSS SAID OUTPUTS, SAID RESISTORS BEING CONNECTED TOGETHER TO PROVIDE A JUNCTION; AND A VARIABLE RESISTOR COUPLED TO SAID JUNCTION BETWEEN SAID RESISTORS, SAID VARIABLE RESISTOR HAVING AN ADJUSTABLE WIPER CONNECTED TO GROUND, SAID PAIR OF RESISTORS, SAID VARIABLE RESISTOR AND SAID INHERENT CAPACITANCE PROVIDING VARIABLE RESISTANCECAPACITANCE CIRCUITS TO CONTROL BASS FREQUENCIES. 